4-A

It's pretty easy to get the first Star Coin. While on the paddle wheel, simply jump while the platform is high. For an extra boost, you can bounce off of one of the flying koopas, but that trick isn't necessary.

After nabbing the first Star Coin, you'll move to another paddle wheel area that's guarded by flying koopas. Before jumping onto the wheel, look above to spot the tail end of a vine. To reach it, jump forward and bounce off the top of the green flying koopa. Be sure to hold UP on the controls as you approach the vine, letting you swing to an area with the next Star Coin.

Just before the stage's end is a set of three pipes that form a stairway leading to the final area. You can duck into the first pipe to reach a hidden area with the final Star Coin. Wall jump to grab it (and watch out for the piranhas!).

There are odd wheel platform formations floating in the various bodies of water of this stage. By standing on the platforms, you can move the wheel to effectively drive across the water. You'll need to use this technique to make it across some large stretches of poisonous water.

When getting ready to grab the second Star Coin, knock the red koopa from his shell pick up the shell as a weapon. Stomp on the P Switch when the non-brick platform is clear of enemies and all of the koopas will fall to the ground. Kick the koopa shell down into the pit of enemies and it'll clear 'em all in one sweep, giving you a 1-Up.